The acronym said it all: MAD. From the late 1940s until the late 1980s, the unthinkable idea of “mutual assured destruction” was the centerpiece of the cold war. You may recall how it worked: Automatic retaliation in a nuclear war would be so destructive that both sides would lose everything.

Nuclear weapons became a kind of “pagan god,” a Monitor editorial observed on the 40th anniversary of the bomb blast at Hiroshima. And “to appease this insatiable nuclear deity, more and deadly nuclear weapons are made and deployed – as if it must be fed and placated to keep it from unleashing nuclear wrath upon the people.”

Was MAD crazy? If everything the human race ever does is rational, then the threat of Armageddon was off the charts wacko. But MAD arose in a century that had already produced two world wars, unprecedented genocide, saturation bombing, and any number of other shameful chapters. MAD was not especially odd in that lineup. Perverse as it seems, the assurance of mutual destruction in the second half of that century may have been the reason that Aug. 9, 1945, was the last time a nuclear weapon was detonated in an international conflict.

A South Asian diplomat who has had firsthand dealings with Iranian leaders recently observed that Iranians have a fairly normal desire to assert themselves as a nation. They see India, Pakistan, and Israel with nuclear weapons and don’t accept that they should be blocked. Their isolation, which is growing under a tough international sanctions regime, intensifies their sense of both defensiveness and entitlement.

We don’t know if Iran will go nuclear, but it appears to be gaining the scientific and industrial ability to do so. Attempts to stop Iran’s nuclear program through stealth or outright attack would, at best, only delay it. So let’s think the unthinkable for a minute. Let’s think about Iran getting the Bomb.

If Iran’s leaders are rational, self-interest should keep them from doing anything rash, knowing they would face massive retaliation. But there is a troubling undercurrent in Iranian thinking. President Mahmoud Ahmadinejad and other Iranian leaders love to make apocalyptic threats, especially about the destruction of Israel. These are often wrapped into an eschatological vision involving the return of the Maadi, or 12th imam, of Shiite Islam, who is believed destined to wage an all-out holy war in which Islam will prevail. Iranian Shiism also glorifies martyrdom. Add the A-bomb and you can see why Israelis and many others are concerned that mutual assured destruction might not work with Iran.

No one can say whether Iran’s threats are a clear and present danger or just political theater. But one thing Iran has in common with all other countries is that it is made up of millions of people interested in living a good life, building businesses, and raising families. It would take a very mad leader to rain down destruction on all those lives in the hopes of proving a theological point.

Similar concerns about irrational ideologies and dark intentions were present when the USSR and China got the Bomb. Nuclear war with Russia or China is not unthinkable today, but it is far-fetched, even though we still live in a world where the United States has 8,500 nuclear weapons, Russia has 11,000, and China and six other nations have hundreds more. While MAD was the first, crude effort to keep nuclear ambitions in check, diplomacy, cultural exchanges, and trade have worn away suspicions over time.

Although that pagan god is still being fed and placated in the Middle East today, the rest of the world has largely walked away from it.That Monitor editorial marking 40 years after Hiroshima said it best: “Mankind cannot for long be intimidated into peace.”